A case-control study confirms that microsatellite assay can identify patients at risk of developing oral squamous cell carcinoma within a field of cancerization

Distinguishing true precursor lesions on the basis of clinical or histologi cal features alone is unreliable but is important so that appropriate inter vention can he instigated, Preliminary studies have shown that a microsatel lite assay mag provide important new prognostic information, To build on th ese observations, we have performed a case-control study to establish wheth er we can be confident about incorporating this new information into clinic al practice, We have determined the frequency of allelic imbalance (AI) wit hin key chromosomal regions, by matching 39 cases with dysplastic oral lesi ons that developed a tumor on the same side of the mouth, for as many varia bles as possible, with controls presenting with similar lesions that did no t progress to malignancy when followed for the same period. Our findings co nfirm that the group that developed tumor had precursor lesions that harbor AI at more loci (P = 0.002). However, no consistent patterns of AI were as sociated with the three grades of dysplasia: mild, moderate, and severe, On e-third of the tumors developed at the same site as the dysplastic lesion a nd two-thirds at a different site, which revealed that the presence of thes e aberrations in a dysplastic lesion provided information about the risk of malignant change within a larger field. This suggests that the process of field cancerization is more widespread than previously recognized. On the b asis of these findings, we advocate complete excision of all suspicious are as that show At at two or mure hey loci, regardless of the degree of dyspla sia. However, because the remaining mucosa is also "at risk," these eases s hould also be targeted to receive dietary advice and chemoprevention, to mi nimize their risk of tumor formation at a distant site.